Chapter 7, Problem 75E

Element First Ionization Energy (kJImol) Second Ionization Energy (kiImol) I

K

419

3050

Ca

590

1140

75. Use principles of atomic structure to answer each of the following:

(a) The radius of the Ca atom is 197 pm; the radius of the ${\text{Ca}}^{2+}$ ion is 99 pm. Account for the difference.

(b) The lattice energy of $\text{CaO}\left(s\right)$ is −3460 kJ/mol; the lattice energy of ${\text{K}}_2\text{O}$ is −2240 kJ/mol. Account for the difference.

(c) Given these ionization values, explain the difference between Ca and K with regard to their first and second ionization energies.

Element	First Ionization Energy (kJ/mol)	Second Ionization Energy (kJ/mol)
K	419	3050
Ca	590	1140

(d) The first ionization energy of Mg is 738 kJ/mol and that of Al is 578 kJ/mol. Account for this difference.